This invention relates to a screw compressor, and more particularly to a screw compressor having two compressors, that is, a high-pressure stage compressor and a low-pressure stage compressor.
One conventional package-type screw compressor is disclosed in JP-A-6-101669. In the package-type screw compressor disclosed in this publication, compressors, a speed increasing gear and a main motor are mounted on a base in order to facilitate the inspection and maintenance operation and also to reduce an installation space, including a maintenance space to a minimum. An intercooler, an aftercooler, an oil cooler and a coolant cooler are arranged in a direction perpendicular to the axis of the motor so that tube nests of the air coolers can extend in the same direction. An operation panel with a maintenance display is provided on a front panel surface of a soundproof cover, and a door panel is of a double hinged type. With this construction, the daily inspection is carried out in a concentrated manner through the front panel surface and its adjoining side panel.
In the above conventional screw compressor, although the daily inspection of this screw compressor can be easily effected, the various equipments, forming the screw compressor, must be provided as separate units so as to be arranged for facilitating the maintenance, and as a result the number of the component parts are inevitably increased. Particularly, because the intercooler and the aftercooler are provided as the separate units and because there are needed pipes for connection of the compressors, forming the high-pressure stage and the lower-pressure stage, to the respective coolers, the number of the component parts naturally increases.
Further, in the package-type screw compressor, disclosed in the above publication, the air, compressed in the compressor body, is introduced into a cooling tube of each of the coolers, and the outer side of the cooling tube is cooled by cooling water. As a result, the coolers are increased in size although the cooling performance for the compressed air is enhanced. Therefore, there has been need for a package-type screw compressor in which each of coolers is made compact while maintaining the cooling performance at a currently-available level.
The present invention has been accomplished in view of the problems of the above conventional screw compressor, and it is an object of the invention to realize a screw compressor in which the number of component parts is reduced, thereby enhancing the assembling ability.
Another object of the invention is to realize a screw compressor which is compact and economical by reducing the number of the component parts.
A further object is to improve the maintenance ability of a screw compressor.
The invention seeks to attain at least one of these objects.
The first feature of the invention for attaining the objects is that, in a screw compressor comprising an electric motor having a bull gear mounted on an end of a shaft of the motor, a first stage compressor and a second stage compressor, each of which includes a male rotor with a pinion mounted on an end of its shaft and meshing with the bull gear, a speed increaser casing for accommodating the bull gear and the pinions, an intercooler for cooling the air compressed by the first stage compressor, and an aftercooler for cooling the air compressed by the second stage compressor, a casing of the intercooler, a casing of the aftercooler and the speed increaser casing are formed integrally with one another.
Preferably, the integral casing is made of a casting or molding, and the intercooler and the aftercooler have a cooler nest, and cooling water flows in a tube of the cooler nest while the compressed air flows outside of the tube; the integral casing has a generally L-shaped cross-section, the intercooler and the aftercooler are disposed adjacent to each other, and a space is formed for separating the two coolers and the speed increaser casing; flow passages, connecting the first and second stage compressors to the intercooler and the aftercooler, are formed in the integral casing; and the cooler nest is removably mounted on the integral casing, and the cooler nest can be removed in a direction substantially perpendicular to an axis of rotation of the motor.
Preferably, an oil tank portion for collecting lubricating oil for the pinions and the bull gear is formed at a lower portion of the speed increaser casing, and an oil pump for supplying the lubricating oil, collected in the oil tank portion, to the pinions and the bull gear, as well as an oil cooler for cooling the lubricating oil, is mounted on the speed increaser casing; a suction device for introducing gas from the interior of the speed increaser casing, and an oil-separating filter is provided between the speed increaser casing and the suction device; an ejector is provided for introducing gas from the interior of the speed increaser casing; and during the operation of the screw compressor, the interior of the speed increaser casing is kept at a pressure lower than the atmospheric pressure.
The second feature of the invention for attaining the objects is that, in a screw compressor comprising a first stage compressor, an intercooler for cooling working air compressed by the first stage compressor, a second stage compressor for compressing the working air cooled by the intercooler, and an aftercooler for cooling the compressed air compressed by the second stage compressor, in which a power of an electric motor is transmitted to the first and second stage compressor via speed increasing gears, an integral casing is provided, which together with the first and second stage compressors, includes all of working gas flow passages through which the working gas, drawn into the first stage compressor, flows out from the aftercooler.
Preferably, the integral casing includes a speed increaser casing for housing the speed increasing gears; the integral casing includes a casing of the intercooler and a casing of the aftercooler, and the intercooler and the aftercooler have a cooler nest, in which the working air flows outside of a tube of the cooler nest while cooing water flows in the tube; the integral casing includes a first stage discharge passage for connecting the first stage compressor to the intercooler, a second stage intake passage for connecting the intercooler to the second stage compressor, and a second stage discharge passage for connecting the second stage compressor to the aftercooler; an intake port for feeding the working air to the first stage compressor and a discharge port for feeding the working air, cooled by the aftercooler, to the consumer are formed in the integral casing; and the intercooler and the aftercooler are disposed adjacent to each other, and the two coolers are spaced from the speed increaser casing.
The third feature of the invention for attaining the above objects is that in a screw compressor comprising at least one stage compressor, a capacity control valve provided upstream of the first stage compressor, a check valve provided downstream of the final stage compressor, a blow-off valve capable of releasing discharge air, discharged from the final stage compressor, to the ambient atmosphere from a location between the final stage compressor and the check valve, and an aftercooler for cooling the discharge air discharged from the final stage compressor, a secondary side of the blow-off valve is connected to a primary side of the capacity control valve, and an integral casing is provided, which together with the first and second stage compressors, includes all of working gas flow passages through which the working gas, sucked into the first stage compressor, flows out from the aftercooler. Preferably, the blow-off valve is disposed between the aftercooler and the check valve; and the blow-off valve and the check valve are integrally incorporated in the capacity control valve.